As portable electronic terminals and other devices are becoming smaller and thinner, thin and bendable flexible printed circuits are being widely used as circuits installed in such devices.
Known flexible printed circuits, in general, include those having a structure in which a ground circuit made of, for example, copper is formed on a surface of, for example, a polyimide film and components, such as connectors, are mounted on a portion of the circuit.
In many cases, such flexible printed circuits typically include a metal reinforcement sheet attached to the back surface, opposite to the mounting surface, via, for example, an electrically conductive adhesive in order to prevent connection failure when mounting components and to prevent the components from becoming detached over time. Such a metal reinforcement sheet may be made of, for example, a stainless steel sheet and have a thickness of more than 50 μm (see, for example, Patent Literature 1).
In the case that such a thick reinforcement sheet is provided, however, the flexible printed circuit and an electronic device in which the flexible printed circuit is installed are inevitably thick. Thus, there are cases in which it is impossible to contribute to a thickness reduction of electronic devices and other devices, which is desired in the industry.
In view of contributing to such a thickness reduction, when only an electrically conductive adhesive is used without using a thick metal reinforcement sheet, there are cases in which warping of the flexible printed circuit occurs as a result of shrinkage during curing of the electrically conductive adhesive.
On the other hand, for flexible printed circuits, there is a known method for preventing the generation of noise due to the influence of electromagnetic waves. In the method, the ground circuit and other members are electrically connected to each other by using electrically conductive tape (see, for example, Patent Literature 1).
However, in the circumstance in which a thickness reduction of electronic devices and other devices and a higher level of electrical conductivity are desired, there are cases in which the use of only an electrically conductive adhesive, without the use of a thick metal reinforcement sheet, results in a level of electrical conductivity slightly below the level of electrical conductivity desired in the industry, which results in a failure to exhibit good electromagnetic wave shielding characteristics.